Power Tripping Query

RunAgroundHard

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Twice this weekend the battery power has tripped. Switching off all breakers and switching back on restores power.

The first time there was no warning, the second time, the DSC alarm sounded for a few seconds, < 5s, then stopped. That was when I noticed the plotter and instruments had stopped working.

The boat is 24V, but the VHF, Raymarine Axiom+ 12, ST60s and ICS Nav 6 are all 12V. I know for a fact that these tripped. 12V DC is from the BEP “DCVR 20A Switchmode DC Voltage Converter”. The BEP device is old, probably over 25 years old. I am less sure if the 24v side stopped as I did not test that.

The first time it tripped I was testing a dinghy inflator by clipping the crocodile clips to the +12V bus bar and the common -ve bus bar. The dinghy inflater failed to operate when the button was pushed. I am wondering if there was an issue with that device that caused the trip that time. No DSC alarm, no warning, just noticed when I went on deck that the plotter was off.

The second time was after I connected the shore power. The Sterling battery charger came on, settled down and a few minutes later the DSC alarm briefly sounded and then stopped when the power tripped. Maybe the VHF initiated a low voltage alarm immediately before the trip.

The switch circuit breakers in the panel never tripped to the off position. By switching off the power to the panel by flicking the 12V and 24V breaker off then back on, all started working again. Before this I switched all breakers off, reseting after the 22/24 flipping step. There is no inverter, just the Sterling charger.

I am guessing that the 12V breakers did not trip as there was no fault, but the BEP shutdown because there is a fault in that.

What do you think?
 

KompetentKrew

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This reminds me of a problem I had which turned out to be knackered 12v isolator switch - it seems like the connection was made but there was a bit of resistance, so the voltage dropped too low when the mains went off. Switching it off and on worked for a while and then it failed completely.

You can get weird stuff happening with low voltage DC systems, especially when they're 25 years old, like ours. Corrosion on my boat's main fuse / holder caused the inverter not to work, because the combination of the inverter's power draw and the corrosion on the main fuse dropped the voltage to below the inverter's safety cut out level.

I feel like you should be looking in the region of the BEP 24v -> 12v converter.

In my experience bugs like these make no sense at all until they do - it's like chasing a poltergeist. You think you've found the cause and you think "right I'll do this to test it" but that doesn't behave as expected so you're even more mystified - then when you do eventually find the cause it all suddenly clicks into place, does make sense and you can prove it to yourself (by hotwiring the 12v breaker with a metal bulldog clip, for example, or even the main fuse for a few minutes).
 

Alex_Blackwood

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Twice this weekend the battery power has tripped. Switching off all breakers and switching back on restores power.

The first time there was no warning, the second time, the DSC alarm sounded for a few seconds, < 5s, then stopped. That was when I noticed the plotter and instruments had stopped working.

The boat is 24V, but the VHF, Raymarine Axiom+ 12, ST60s and ICS Nav 6 are all 12V. I know for a fact that these tripped. 12V DC is from the BEP “DCVR 20A Switchmode DC Voltage Converter”. The BEP device is old, probably over 25 years old. I am less sure if the 24v side stopped as I did not test that.

The first time it tripped I was testing a dinghy inflator by clipping the crocodile clips to the +12V bus bar and the common -ve bus bar. The dinghy inflater failed to operate when the button was pushed. I am wondering if there was an issue with that device that caused the trip that time. No DSC alarm, no warning, just noticed when I went on deck that the plotter was off.

The second time was after I connected the shore power. The Sterling battery charger came on, settled down and a few minutes later the DSC alarm briefly sounded and then stopped when the power tripped. Maybe the VHF initiated a low voltage alarm immediately before the trip.

The switch circuit breakers in the panel never tripped to the off position. By switching off the power to the panel by flicking the 12V and 24V breaker off then back on, all started working again. Before this I switched all breakers off, reseting after the 22/24 flipping step. There is no inverter, just the Sterling charger.

I am guessing that the 12V breakers did not trip as there was no fault, but the BEP shutdown because there is a fault in that.

What do you think?
First thing , not to do, is leap in and reset the breakers. You say that you are unsure if you lost 24V or not. You need a multimeter or even a test lamp and when the fault occurs, without touching anything work from one end of the system to the other. e.g. Do you get voltage at the switch panel and is it full 12volt, do you have an output from the BEP, again is it full voltage? Do you have input to the BEP, again what level. You may find a complete loss of power or in the case of a bad connection a low voltage reading. You need to be methodical as trying everything at once will just confuse the issue. I would have thought it likely to be a bad connection(s) as a component fault in the BEP would cause permanent failure.
Having said that you can never be 100% sure. It also wouldn't do any harm to run through the above with the system operating correctly. you might just find a discrepancy in readings that could indicate a potential fault.
 

Alex_Blackwood

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That’s the thing, the circuit breakers are not tripping. When I flip the 12 and 24 breakers, it’s from on to off to on again,

I will check all the connections.
I understand. However if you have a bad connection or contact in a breaker or switch and you turn "ON" "OFF" "ON" you may reset that connection. When you have the fault try to trace it without touching or altering the setup. Depending which end of the circuit you start at you are looking for the point where you lose the voltage or it appears. i.e. If you start at the battery you should have voltage until you reach the faulty unit, you then may have it at the input but not the output.
 
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